Effects of polyunsaturated fatty acids and their n-6 hydroperoxides on growth of five malignant cell lines and the significance of culture media

We examined effects of polyunsaturated fatty acids (PUFA), their corr esponding hydroperoxy fatty acids (hp-PUFA), as well as various pro- and antioxidants on the growth of tumor cells in culture. When cultur ed in RPMI 1640 medium, A-427 and WEHI clone 13 cells were both highl y sensitive to hydroperoxy docosahexaenoic acid (hp-DHA), but they we re far less sensitive in minimum essential medium (MEM). In contrast, A-427 cells were also sensitive to DHA in both culture media, while WEHI clone 13 cells, as well as other cell lines, tested in their res pective media, were resistant. The lower sensitivity of the cell line s to hp-DHA in MEM-medium was apparently due to a more rapid reductio n of hp-DHA to the corresponding hydroxy-DHA in MEM-medium. Addition of glutathione (GSH) to the culture medium abolished the effects of h p-DHA, but not the effects of DHA, while depletion of intracellular G SH levels by L-buthionine-S,R-sulfoximine strongly enhanced the cytot oxic effect of hp-DHA, but not the cytotoxic effect of DHA. alpha-Toc opherol protected A-427 cells against the toxic effect of DHA and abo lished the induced lipid peroxidation, while it did not protect again st the toxic effects of hp-DHA in A-427 or WEHI clone 13 cells. Ascor bic acid reduced the cytotoxic effect of DHA, but potentiated the tox ic effect of hp-DHA while selenite essentially abolished the toxicity of both DHA and hp-DHA. These results indicate that sensitivity of t umor cell lines to PUFA and their oxidation products depends on their antioxidant defense mechanisms, as well as culture conditions, and e stablishes hp-DHA as a major, but probably not the sole, metabolite r esponsible for cytotoxicity of DHA.